Quantifying China's carrying capacity : using optimization to explore sustainable food production

Abstract

Feeding the world's growing population in an environmentally sustainable way is a complex social and engineering challenge. In this thesis, we develop a novel method for assessing the number of people that can be fed sustainably in a particular region for given natural resources and diet (the carrying capacity). A quantitative assessment of carrying capacity provides insight into the food security of the study region as well as the stress on the environmental system; in addition, this methodology can be used to assess the carrying capacity under a variety of policy interventions such as increasing yields, changing diets, or expanding irrigation infrastructure. The carrying capacity assessment uses optimization methods that find the cropping pattern that maximizes population subject to land, water, and diet constraints, considering a range of rainfed and irrigated crops. A data fusion procedure estimates the regional water and land resources needed to assess carrying capacity by combining measurements from diverse hydrologic and agronomic sources, including remote sensing data. Our carrying capacity methodology is illustrated with a case study of food security in China. China has historically been largely food self-sufficient, although its food imports have been increasing since the year 2000. We find that the population in China was well below the country's carrying capacity in the year 2000 given the diet and yields in that year. However, the population's changing diet - especially the growing preference for meat - is exacting a growing toll on land and water resources. We find that under a more recent diet (2013), China is not likely to be food self-sufficient, even with major investments in irrigated agriculture, without substantial increases in crop yield.